Apparatus for electroplating the inner surface of a tubular article



Ap 1955 c. E. LICHARZ APPARATUS FOR ELECTROPLATING THE INNER SURFACE OF A TUBULAR ARTICLE Filed March 8. 1950 INVENTOR. v A-Z vMe 410/442 2:;

Cam B Y k APPARATUS FOR ELECTROPLATING THE INNER SURFACE OF A TUBULAR ARTICLE Carl Elmar Licharz, Stockholm, Sweden, assignor to glectro Metal Hardening Co. S. A. Tanger, Paris,

rance the inner surface of a tubular article.

An ob ect of the invention is to provide an arrangement for electroplating the inner surface of a tubular article by means of which the circulating electrolyte used for the electroplating of the article serves also as cooling means for the anode.

Another object of the invention is to provide an arrangement for electroplating the inner surface of a tubular article by means of which a high quality of electroplating may be obtained.

A further object of the invention is to improve on arrangements for electroplating the inner surface of tubular articles as now ordinarily made.

Other objects and structural details of the invention will be apparent from the following description when read in conjunction with the accompanying drawing forming part of this specification, which illustrates a longitudinal sectional view of a tube to be electroplated with the anode disposed centrally therein.

The walls c of a hollow cylindrical tube to be internally chrominum plated are connected to a cathode current conductor k. At the upper and lower ends the tube is hermetically sealed by means of rigid end wall means or covers 1 consisting of suitable insulating material which is resistant against the chromic acid bath. The covers I also serve to carry the anode e disposed with its axis centrally in the tube. In the embodiment shown the anode e consists of an internal, hollow lead tube 1 through which the electrolyte enters at m. The lead tube 1 is surrounded by a copper tube g which in turn is provided with a lead cover h. The electrolyte flowing through the hollow interior of the anode is in contact exclusively with the lead tube 1, and the electrolyte within the tube only comes into contact with the outer lead cover h of the anode. The flow of the circulating electrolyte from the interior of the anode e to the chamber between the anode and the tube 0 takes place through passage means or apertures b arranged in the anode e in substantial proximity to the lower cover I. As these apertures b also extend through the intermediate copper tube g of the anode it is necessary to provide the apertures with a protective coating, preferably of lead. This protective coating can be applied either electrolytically, by spraying or in any other suitable way.

In the embodiment shown the electrolyte flows downwardly from the inlet m through the lead tube 1 which forms the internal passage of the anode e, through the apertures b at the lower end of the anode into the chamber between the anode and the tube e; the electrolyte then flows upwardly and is removed through the outlet tube d in the upper cover. The supply of electric current to the anode e is effected in the embodiment shown by way of conductors i which are directly connected to the copper tube g which projects beyond the outer lead cover b. In this way the current is caused to fiow mainly through the copper which has a high conductance whereby heat ing of the anode is reduced as much as possible. Moreover the fresh electrolyte flowing through the interior of the anode exerts, a cooling effect upon the anode. Where a long anode is used it is preferable to arrange the supply of electric current at each end of the anode thereby securing uniform current distribution.

According to the embodiment shown in the drawing the chromium plating of the internal surface of the tube is performed with the tube disposed vertically. This method United States Patent 0 2,706,175 Patented Apr. 12, 1955 'ice has proved to be particularly advantageous as the removal of hydrogen produced by the electrolysis, is facilitated, the hydrogen being discharged together with the outflowing electrolyte through the outlet tube d. If the chromium plating method according to the invention is applied to horizontally disposed tubes of greater dimensions a greater number of apertures is preferably provided in the anode, these apertuers being preferably evenly distributed over the whole length of the anode.

The electrolyte discharged through the outlet tube d flows to a container (not shown) where chromic acid is added as necessary in order to maintain the concentration of chromium in the electrolyte. The regenerated electrolyte is thereafter recirculated from the container to the interior of the anode by means of a pump built of chromic acid resistive material.

The internal plating obtained by the process according to the invention is preferably freed from confined hydrogen and I have found that this may, for example be effected by subjecting the interior of the tube to a high vacuum, for example 0.001 Torricelli; the treatment may for example be carried out for about one hour when the greater part of the hydrogen will have been removed. Any residual hydrogen may if desired, be removed by subjecting the tube to slow heating, the temperature being kept below the annealing point of the metal.

In this way a practically hydrogen free chromium-coating is obtained on the metal without the necessity of applying such temperatures for removing the hydrogen as would impair the firmness and rigidity of the chromium deposit and its firm adherence to the underlying metal.

It is to be understood that the above description of certain embodiments of the invention is only illustrative, the full scope of the invention vbeing defined in the appended claims.

What I claim is:

1. An arrangement for electroplating the inner surface of a tubular article, comprising in combination: a hollow anode having a closed end and an open end for connection with the electrolyte supplying means, first end Wall means having its major surface transverse to the longitudinal axis of said anode and being connected to said anode adjacent said closed end thereof, second end wall means having its major surface transverse to the longitudinal axis of said anode and being connected to said anode adjacent said open end thereof, said first and said second end wall means being arranged to receive therebetween the tubular article to be electroplated and tightly closing the open ends of said article so as to form with said tubular article and said anode a chamber for receiving an eloctrolyte from the interior of said anode, said anode having a smooth outer wall and being provided with passage means intermediate said first and second end wall means and arranged only in substantial proximity to said first end Wall means and extending from the inside of said anode to the outside thereof for conveying electrolyte in substantial proximity to said first end wall means from inside said anode to said chamber, and electric current conducting means connected to said article and at least one end of said anode, said second end wall means being provided with passage means extending therethrough for Withdrawing electrolyte from said chamber whereby the electrolyte is led through the interior of said anode in one direction of fiow, thereby elficiently cooling said anode, and then passes through said passage means into said chamber in counterfiow to said one direction.

2. An arrangement according to claim 1 in which the anode includes a copper tube having a length greater than the distance between the insides of said end wall means, a lead tube covering the inside of and being connected to said copper tube, said lead tube having a length at least equalling the length of said copper tube, and a lead coating covering the outside of said copper tube between the insides of said first and second end wall means, the passage means extending through said anode having a lead coating throughout the length of said last mentioned passage means thereby preventing electrolyte passing therethrough from contacting said copper tube.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Meyer Mar. 9, 1909 Bohlman June 16, 193 1 6 Olin et al. Nov. 1, 1932 Fiedler Sept. 19, 1933' McKinney et a1 Nov. 27, 1934 '4 Greenslade Oct. 26, 1943 Martz Dec. 2, 1947 Bartlett July 12, 1949 FOREIGN PATENTS Great Britain Feb. 8, 1904 France Nov. 27, 1937 

1. AN ARRANGEMENT FOR ELECTROPLATING THE INNER SURFACE OF A TUBULAR ARTICLE, COMPRISING IN COMBINATION: A HOLLOW ANODE HAVING A CLOSED END AND AN OPEN END FOR CONNECTION WITH THE ELECTROLYTE SUPPLYING MEANS, FIRST END WALL MEANS HAVING ITS MAJOR SURFACE TRANSVERSE TO THE LONGITUDINAL AXIS OF SAID ANODE AND BEING CONNECTED TO SAID ANODE ADJACENT SAID CLOSED END THEREOF, SECOND END WALL MEANS HAVING ITS MAJOR SURFACE TRANSVERSE TO THE LONGITUDINAL AXIS OF SAID ANODE AND BEING CONNECTED TO SAID ANODE ADJACENT SAID OPEN END THEREOF, SAID FIRST AND SAID SECOND END WALL MEANS BEING ARRANGED TO RECEIVE THEREBETWEEN THE TUBULAR ARTICLE TO BE ELECTROPLATED AND TIGHTLY CLOSING THE OPEN ENDS OF SAID ARTICLE SO AS TO FORM WITH SAID TUBULAR ARTICLE AND SAID ANODE A CHAMBER FOR RECEIVING AN ELECTROLYTE FROM THE INTERIOR OF SAID ANODE, SAID ANODE HAVING A SMOOTH OUTER WALL AND BEING PROVIDED WITH PASSAGE MEANS INTERMEDIATE SAID FIRST AND SECOND END WALL MEANS AND ARRANGED ONLY IN SUBSTANTIAL PROXIMITY TO SAID FIRST END WALL MEANS AND EXTENDING FROM THE INSIDE OF SAID ANODE TO THE OUTSIDE THEREOF FOR 